Concrete is a relatively brittle material that exhibits poor tensile strength. A known way to enhance the toughness and energy absorption capacity of concrete is to disperse short fibers, often made from steel, throughout the concrete. The fibers are typically provided with one or more deformations that allow them to more effectively anchor in the cement matrix.
A typical fiber construction is shown for example in U.S. Pat. No. 5,215,830 issued Jun. 1, 1993 to Cinti. Cinti discloses a fiber with a substantially straight central portion and two end portions that are laterally offset from the central portion. The end portions are both offset towards the same side of the fiber.
An alternative arrangement is disclosed in U.S. Pat. No. 5,451,471 issued Sep. 19, 1995 to Over et al. The fiber disclosed in Over et al. has flattened portions arranged along its length. The flattened portions are shown as being coplanar, although the patent suggests that they could instead be alternately rotated a quarter turn. Over et al. does not suggest rotating the flattened portions at any angles other than 90 degrees, and no indication is given as to whether the disclosed 90 degree rotation would have any advantageous effects. Nor does the patent provide any test results in this regard.